Question

Arrange the following in increasing order of acid strength: phenol, ethanol, water.

Hint:

The acidity of alcohols and phenols increases with the ability to stabilize the conjugate base. Phenols are more acidic due to the resonance stabilization of the phenoxide ion.

Answer 1

To arrange these compounds in increasing order of acid strength, we consider the ability of these compounds to donate a proton. The stronger the ability to donate a proton (H\(^+\)), the stronger the acid.
1. Ethanol (CH\(_3\)CH\(_2\)OH): Ethanol has a hydroxyl group (-OH) but it is a very weak acid compared to water or phenol.
2. Water (H\(_2\)O): Water is neutral but can act as a weak acid, donating a proton to form \( OH^- \).
3. Phenol (C\(_6\)H\(_5\)OH): Phenol is a stronger acid than both ethanol and water due to the resonance stabilization of the phenoxide ion (C\(_6\)H\(_5\)O\(^-\)) after proton donation.
Thus, the increasing order of acid strength is: \[ \text{Ethanol} < \text{Water} < \text{Phenol} \]